Commit 1aaac071 authored Aug 17, 2013 by Rafael J. Wysocki

ACPI / hotplug / PCI: Fix NULL pointer dereference in cleanup_bridge()

After commit bbd34fcd (ACPI / hotplug / PCI: Register all devices
under the given bridge) register_slot() is called for all PCI
devices under a given bridge that have corresponding objects in
the ACPI namespace, but it calls acpiphp_register_hotplug_slot()
only for devices satisfying specific criteria. Still,
cleanup_bridge() calls acpiphp_unregister_hotplug_slot() for all
objects created by register_slot(), although it should only call it
for the ones that acpiphp_register_hotplug_slot() has been called
for (successfully). This causes a NULL pointer to be dereferenced
by the acpiphp_unregister_hotplug_slot() executed by cleanup_bridge()
if the object it is called for has not been passed to
acpiphp_register_hotplug_slot().

To fix this problem, check if the 'slot' field of the object passed
to acpiphp_unregister_hotplug_slot() in cleanup_bridge() is not NULL,
which only is the case if acpiphp_register_hotplug_slot() has been
executed for that object. In addition to that, make register_slot()
reset the 'slot' field to NULL if acpiphp_register_hotplug_slot() has
failed for the given object to prevent stale pointers from being
used by acpiphp_unregister_hotplug_slot().

Reported-and-tested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent d010e576

drivers/pci/hotplug/acpiphp_glue.c

+3 −1

Original line number	Original line	Diff line number	Diff line
	@@ -340,6 +340,7 @@ static acpi_status register_slot(acpi_handle handle, u32 lvl, void *data,

	retval = acpiphp_register_hotplug_slot(slot, sun);		retval = acpiphp_register_hotplug_slot(slot, sun);
	if (retval) {		if (retval) {
			slot->slot = NULL;
	bridge->nr_slots--;		bridge->nr_slots--;
	if (retval == -EBUSY)		if (retval == -EBUSY)
	warn("Slot %llu already registered by another "		warn("Slot %llu already registered by another "
	@@ -429,6 +430,7 @@ static void cleanup_bridge(struct acpiphp_bridge *bridge)
	err("failed to remove notify handler\n");		err("failed to remove notify handler\n");
	}		}
	}		}
			if (slot->slot)
	acpiphp_unregister_hotplug_slot(slot);		acpiphp_unregister_hotplug_slot(slot);
	}		}